In recent years, along with the advance of miniaturization of MIS transistors configuring semiconductor integrated circuits, thinning of a gate insulating film of MIS transistor made of silicon oxide has been advanced rapidly. Meanwhile, when the film thickness of the gate insulating film gets thinner, due to a quantum effect called direct tunneling, a gate leakage phenomenon gets significant, in which electrons in a silicon substrate are escaped through the gate insulating film to a gate electrode.
To get around this problem, a study to replace the gate insulating film material by an insulating material (high-k material) having a relative permittivity (dielectric constant) higher than that of silicon oxide (SiO2) has been considered. This way is advantageous because the actual physical film thickness can be increased by multiplying [permittivity of the high-k film divided by permittivity of the silicon oxide film] by itself when the gate insulating film is formed of a high-k material, even with a same equivalent silicon oxide film thickness, resulting in a reduction of the gate leakage current. As a high-k material, hafnium oxide and aluminum oxide have been considered, for example.
In addition, one example of a method of depositing a film having a thin film thickness as a gate insulating film with excellent controllability is ALD (Atomic Layer Deposition) method. Technologies regarding this ALD method are disclosed in, for example, Japanese Patent Application Laid-Open Publication No. 2006-169556 (Patent Document 1) and Japanese Patent Application Laid-Open Publication No. 2005-235967 (Patent Document 2).